The US K-12 educational system is not producing enough skilled graduates to meet future needs for science professionals and a science- and health-literate population. Problems with student achievement in science begin in elementary and middle school. Approaches that provide experiences outside normal school hours offer promise for preparing students for success in high school and beyond. However, despite the clear need to apply all available options to develop students'awareness of, and interest in life sciences and biomedical research, few materials or resources on these topics are tailored specifically for after school programs. Baylor College of Medicine (BCM), in partnership with the Houston Independent School District, the American Physiological Society, and Hopa Mountain (community-based organization serving rural and tribal leaders in the Northern Rocky Mountains and Montana), proposes to develop, evaluate and disseminate a new after school program model that utilizes an informal setting and engaging content to improve middle school students'science learning experiences, skills development and career awareness related to human body systems, infectious disease and allergy research. The model will be implemented and evaluated at five sites across the US with high enrollments of disadvantaged students. Project specific aims are to: (1) recruit and support a national team of teacher leaders, who will work together and with BCM scientists and educators to develop a year-long curriculum and supporting materials for an after school bioscience enrichment program (Bioscience After School) for grades 6-8;(2) evaluate the curriculum and supporting materials, in collaboration with the cadre of teacher leaders and project partners, by implementing after school bioscience enrichment programs in five locations across the US;(3) revise the curriculum and supporting materials, and develop web-based tools-such as discussion forums, streaming video lesson demonstrations and downloadable teaching materials-for teachers who lead Bioscience After School programs;and (4) disseminate all project-related resources (lesson demonstrations, teacher professional development sessions, templates for setting up after school science clubs, and student activities and materials) free-of-charge via the websites, BioEd Online (www.bioedonline.org) and K8 Science (www.k8science.org), and through more traditional pathways. All aspects of the project will be evaluated, both formatively and summatively, to gauge (the quality and effectiveness with which project components are delivered and implemented, and the overall value of the experiences provided to teachers and students.